The present invention relates to an active material for batteries having improved discharge characteristics, which comprises a particular fluorinated graphite.
As fluorinated graphite obtained by reaction of graphite with fluorine, polycarbon monofluoride represented by the formula (CF).sub.n and poly-dicarbon monofluoride represented by the formula (C.sub.2 F).sub.n have been identified, and it is also known that a fluorinated graphite containing both of the above forms exists. However, their actual morphologies have not yet been fully made clear. It is well known, as will be mentioned below, that fluorinated graphite has desirable characteristics as an active material for batteries.
For example, Japanese Unexamined Patent Publication (Tokkyo Kokai) No. 25565/1973 discloses that the use of a solid fluorinated graphite of the formula (CF.sub.x).sub.n in which x is between 0.5 and 1, especially x being equal or close to 1, as an active material for a positive electrode provides a primary battery with a high energy density having a high utilization rate of active material, an excellent voltage flatness and a satisfactory shelf life.
Japanese Unexamined Patent Publication No. 102893/1978 discloses a fluorinated graphite of the formula (C.sub.2 F).sub.n [which will hereinafter be referred to as (C.sub.2 F).sub.n ] and a process for the preparation thereof. The (C.sub.2 F).sub.n does not show an increase of fluorine content even when heated in an atmosphere of fluorine gas at 600.degree. C., and it is also suggested that the (C.sub.2 F).sub.n is used as an active material for batteries. It is also mentioned in Japanese Unexamined Patent Publication No. 28246/1980 that the above (C.sub.2 F).sub.n shows a higher discharge voltage than does the fluorinated graphite of the formula (CF).sub.n [which will hereinafter be referred to as (CF).sub.n ].
Japanese Unexamined Patent Publication No. 84570/1982 proposes the use of a mixture of (CF).sub.n and (C.sub.2 F).sub.n as an active material for a positive electrode to thereby improve the transient drop of voltage in an initial stage of discharge which is the drawback of (CF).sub.n. Japanese Unexamined Patent Publication No. 16468/1983 discloses an active material for batteries predominantly composed of (C.sub.2 F).sub.n obtained by reaction of artificial graphite with fluorine. It is described that the preferred (C.sub.2 F).sub.n -based active material is the product obtained by reaction of artificial graphite with fluorine until there is no increase in weight of the reaction product, and this active material shows a high discharge voltage.
It is an object of the present invention to provide an active material for batteries having an improved discharge voltage.
A further object of the invention is to provide an active material for batteries, which is obtained with an improved productivity.
These and other objects of the present invention will become apparent from the description hereinafter.